与番茄花柄脱落相关的多聚半乳糖醛酸酶的分离纯化和特性

为弄清番茄花柄脱落相关酶—哆聚半乳糖醛酸酶（polygalacturonase,PG）的性质,采用离体培养条件下经乙烯处理的番茄花柄,分离和纯化了多聚半乳糖醛酸酶并测定其性质。结果表明：用Sephadex G-75凝胶过滤层析和CM Sepharose CL-6B阳离子交换层析方法可分离纯化得到分子量约为30．2kDa的多聚半乳糖醛酸酶,纯化倍数为30．85;纯化的PG活性最适pH值为5．0,最适反应温度为40℃;Km值为26．14mg·mL^-1;1mmol·L^-1Ca^2＋、Cu^2＋、Ba^2＋、Co^2＋和Mn^2＋可抑制PG活性,而1mmol·L^-1的Mg^2＋、K^＋、Fe^2＋、Zn^2＋、Fe^2＋促进PG活性,20mmol·L^-1的Fe^2＋和Fe^3＋促进效果尤为显著。     

多聚半乳糖醛酸内切酶的固定化及其性质研究

棉花枯萎病菌多聚半乳糖醛酸内切酶在pH大于7时不稳定,故对它进行多种化学修饰而又不影响其活性,必须在pHd小于7的体系中进行。本文报道将PGAUase在还原剂存在下,与稀酸处理的Sepharose 4B交联,获得较高活力的固定化酶。固定化酶催化动力学表明,最适pH为4,4,最适温度为55℃,在pH1至8.0范围内稳定。和溶液酶比较,对热稳定性提高,但对碱稳定性下降。以多聚半乳糖醛酸为底物,Km为0.27mmol/L,Vmax为66.67nmol/L·min,均大于溶液酶(Km=0.07mmol/L,Vmax=28.00nmol/L·min)。在pH4.8,30℃,聚半乳糖醛酸在固相酶的柱中循环水解不同的时间降解产物经圆盘电泳和等电聚焦测定,得到不同大小的寡糖片段混合物,证明固相酶和溶液酶的作用方式相同,同时使以酶解法制备一定大小的有生物活性的寡糖分子成为可能。     

Endo-PG诱导培养小麦细胞PGIP产生的研究

内切多聚半乳糖醛酸酶（endo-polygalacturonase,endo-PG）是待异水解细胞壁成分多聚半乳糖醛酸的酶,水解产生的10～13个糖基的寡聚半乳糖醛酸片段是活性诱导因子,激活植物自身防御系统．我们已研究发现单子叶植物小麦中存在多聚半乳糖醛酸酶抑制蛋白（polygalacturonaseinhibitingprotein,PGIP）,并已将其分离纯化,对其性质作了初步研究[1,2]文献报导[3]PGIP是在未分化的细胞中合成的．本文报导在悬浮培养的小麦细胞中加入Endo-PG观察其PGIP的生成,比较赤霉病的高抗品种与低抗品种中PGIP的合成情况,探讨PGIP与植物防御作…     

重组菌产碱性果胶酯裂解酶酶学性质研究

利用盐析-透析-色谱流程建立快速高效纯化工程菌E.coli JM109(pHsh PL)所产碱性果胶酯裂解酶(PL)的方法,纯化后酶达到电泳纯,比酶活为1079U/mg.重组菌所产PL酶促反应适宜的pH为9～10,适宜温度为50～66 ℃,与酶基因来源野生菌所产PL相比,重组菌所产PL适宜pH范围有所扩大,并保持了野生菌PL的热稳定性.通过金属离子种类、浓度及存在时间对PL酶活力影响考察发现:在考察的离子中除Mg2 对酶活有较好的促进作用外,其余对重组菌PL均有抑制作用,其中Fe2 对酶活力抑制作用最强.该酶的Km值为20.93 mg/L,Vmax为105.3 μmol/min,反应活化能Ea为21.74 kJ/mol.对重组菌所产PL热稳定动力学进行分析,发现有底物情况下的失活常数kd(0.02 min-1)小于无底物情况下的失活常数kd(0.0342 min-1),说明当酶与底物结合形成复合物时对酶活具有保护作用.利用HPLC-ESI-MS对重组菌所产PL酶解产物进行测定发现,产物含有不饱和二聚半乳糖醛酸(m/z 350.82)和不饱和三聚半乳糖醛酸(m/z 527.04),同时测定结果中没有发现不饱和半乳糖醛酸单体(m/z 175),可以初步推测重组菌PL不能以不饱和二聚半乳糖醛酸和不饱和三聚半乳糖醛酸为底物进一步裂解.     

新鲜大蒜中蒜氨酸酶的分离纯化及性质

用葡聚糖凝胶G-200层析柱分离纯化了新鲜大蒜(Allium sativum)中的蒜氨酸酶, SDS-PAGE结果为单一条带, 分子量为53 kD在35 ℃下以蒜氨酸为底物, Km为0.693 mmol.L-1, Vmax 为0.353 mmol.min-1, 最适反应温度为30 ℃, 热稳定的温度在50 ℃以下。Zn2+对酶有抑制作用, Mn2+使酶活力增加。     

新鲜大蒜中蒜氨酸酶的分离纯化及性质

用葡聚糖凝胶G-200层析柱分离纯化了新鲜大蒜(Allium sativum)中的蒜氨酸酶,SDS-PAGE结果为单一条带,分子量为53 kD在35℃下以蒜氨酸为底物,Km为0.693 mmol·L-1,Vmax为0.353 mmol·min-1,最适反应温度为30℃,热稳定的温度在50℃以下.Zn2 对酶有抑制作用,Mn2 使酶活力增加.     

多聚半乳糖醛酸酶反义基因在转基因番茄中的表达

番茄的多聚半乳糖醛酸是一种在果实成熟阶段特异性表达的酶。为了研究它在果实成熟中的作用,将其ｃＤＮＡ与花椰菜花叶病毒３５Ｓ启动子嵌合后,以反义基因的形式经农杆菌介导导入番茄植株,进一步分析了反义基因的整合与表达。结果表明,在转基因番茄中,反义基因的表达能明显抑制果实内源多聚半乳糖醛酸酶的活性。     

栗疫病菌不同毒力菌株胞外酶活性和草酸产量的比较

对栗疫病菌不同毒力菌株产生胞外酶的种类、活性和草酸产量以及草酸对多聚半乳糖醛酸酶水解聚果胶酸钙的影响进行了研究。所有供试菌株均未能检测到淀粉酶活性。栗疫病菌在培养中可分泌漆酶,多聚半乳糖醛酸酶、蛋白酶、纤维素酶和脂酶,但不同毒力菌株产生这些酶的能力不同。总的来说,强毒力菌株均可分泌这些酶,且活性强,但弱毒力菌株的酶活性较弱或不分泌这些酶。菌丝产量和草酸产量分析表明,强毒力菌株的草酸产量明显高于弱毒力菌株。菌丝产量与草酸产量没有相关性。在没有草酸盐存在的条件下,多聚半乳糖醛酸酶不能降解聚果胶酸钙。     

青霉菌聚半乳糖醛酸酶基因在毕赤酵母中的表达及酶学性质研究

筛选得到一株能分解果胶的青霉菌(Penicillium sp.),使用简并引物PCR和TAIL-PCR方法从该菌中克隆了一个聚半乳糖醛酸酶基因pgp1.pgp1基因全长1 225 bp,包含2个内含子,其cDNA全长1 104 bp,编码367个氨基酸和一个终止密码子,前18个氨基酸为信号肽序列.将pgp1基因连接pPIC9载体,在巴斯德毕赤酵母表达系统中进行了异源表达.在3L发酵罐水平,培养基中聚半乳糖醛酸酶活力达到700 U/mL.酶学性质测定表明,重组酶蛋白PGP1的最适pH为5.0,在pH4.0 -6.0下处理1h后,剩余酶活力超过90％;最适温度为38℃,以聚半乳糖醛酸为底物,PGP1的Km=(1.172±0.169)mg/mL,Vmax=(0.061±0.002) mg/min/mL.     

1-甲基环丙烯(1-MCP)对油桃果实软化的影响

1-甲基环丙烯(1-MCP)可延缓油桃果实硬度的下降,阻止引起果实软化的细胞物质(淀粉、纤维素、果胶)的降解,抑制与果实软化相关的酶(淀粉酶、纤维素酶、多聚半乳糖醛酸酶)活性。     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.     

肝癌中HBV和HCV基因和抗原的分布及意义

采用原位分子杂交方法检测HCV RNA及HBV X基因;采用免疫组织化学方法研究HCV核心抗原,非结构区C33c抗原及HBxAg在肝细胞肝癌中的定位及分布.结果表明(1)HCV RNA、HBV X基因在肝细胞肝癌组织检出率分别为40%(55/136)和82%(112/136).HCV RNA定位于癌细胞的胞浆内,阳性细胞呈散在、灶状及弥漫分布三种形式;HBV X基因在肝癌细胞中的分布呈胞浆型、核型及核浆型,阳性细胞也呈上述三种分布形式;(2)HCV C33c抗原、核心抗原在肝细胞肝癌中的阳性率为81%(133/164)及86%(141/164).C33c抗原定位于癌细胞及肝细胞的胞浆内;核心抗原既定位于癌细胞核中,又可定位于胞浆中.C33c抗原阳性细胞以灶状分布为主;而核心抗原阳性细     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.